I also think that relic is the best gy hate Card as it is so flexible. It beats RUG and is not so bad against Dredge and Reanimtor. Leyline is better against the last two matchups but with Relic you have a good chance to beat the most popular deck :)
What are your opinions about running Thalia MD? I think Thalia will help us against combo a lot and make a better matchup against blade and other decks with control elements. But I am not sure if cutting 2 Mogg war Marshals and 1 Piledriver for 3 Thalia won't harm your deck strategy. You also lose some red cards and make pyrokinesis weaker (the best sideboard card against aggro).
Another question: I saw that some goblin players have recently cut 2 MWM for 2 Mogg Fanatic as it allows to block against blade decks without letting them get lifegain or counters on their equipments. This seems interesting. But perhaps Mogg fan is not good against other matchups as it lowers your creature count?